1. Field of the Invention
The present invention relates generally to tissue treatment systems and in particular to distribution manifolds for wound treatment.
2. Description of Related Art
Clinical studies and practice have shown that providing a reduced pressure in proximity to a tissue site augments and accelerates the growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but application of reduced pressure has been particularly successful in treating wounds. This treatment (frequently referred to in the medical community as “negative pressure wound therapy,” “reduced pressure therapy,” or “vacuum therapy”) provides a number of benefits, including faster healing and increased formulation of granulation tissue. Typically, reduced pressure is applied to tissue through a porous pad or other manifolding device. The porous pad contains cells or pores that are capable of distributing reduced pressure to the tissue and channeling fluids that are drawn from the tissue. The porous pad often is incorporated into a dressing having other components that facilitate treatment.
Distribution manifolds for delivering reduced pressure treatment are also commonly referred to as reduced pressure dressings, or in the case of treatment of a wound, wound dressings. Such dressings are characterized by structural features that allow fluid flow through the material. For example, one material that is often used as a wound dressing is reticulated, open-cell polyurethane foam. The foam includes a plurality of interconnected pores that allow fluid flow throughout the foam. When a reduced pressure is applied to one area of the foam, this reduced pressure is quickly distributed to other areas of the foam and is easily transmitted to tissues adjacent the foam. One problem with open-cell foams and similar materials is tissue in-growth, which prevents easy removal of the foam following treatment. For open cells foams with pore sizes on the order of 100-1000 microns, in-growth of tissue may occur relatively quickly. As the new tissue enters the pores or cells of the foam, the foam acts as a lattice, and tissue grows within the pores and around the walls and/or starts that form the perimeter of the pores. This effectively attaches the foam to the tissue site, and the foam must be forcibly removed by tearing the new tissue and breaking any bonds that have formed between the tissue and the foam. Not only is this detrimental to the healing process, but the tearing of this tissue may cause discomfort to the patient.
One way to circumvent the problem of tissue in-growth is to increase the frequency of dressing changes. If new dressings are applied with increased frequency, there is less tissue in-growth, and thus less disruption of new tissue upon removing the old dressing. One downside to increased dressing changes is the increased costs associated with materials (i.e. new dressings) and labor. Changing a dressing is labor intensive and diverts the attention of medical personnel from other important tasks. Increased dressing changes also result in more aggravation to patients and their wounds.